Phase equilibria in the binary system Bi2O3-ZnO were studied by quenching technique. Heat-treated compositions were subjected to X-ray diffraction for phase identification, and differential thermal analysis, optical and scanning electron microscopy were used to determine the solid-liquid equilibria occurring in this system. The data thus obtained revealed that incorporation of a small amount of ZnO to the high-temperature face-centered cubic lattice of Bi2O3 leads to the formation of a body-centered cubic solid solution (gamma-Bi2O3), which extends up to a composition of 2.2 mol% ZnO at a temperature near 750degreesC. On cooling, the gamma-Bi2O3 solid solution undergoes a eutectoid transformation at a temperature of 710degreesC to yield the low-temperature monoclinic polymorph of Bi2O3 (alpha-Bi2O3) and Bi38ZnO58. The eutectoid occurs at a composition of 1.8 mol% ZnO. The compound Bi38ZnO58 has a crystal structure analogous to the body-centered cubic gamma-Bi2O3 solid solution and melts incongruently at a temperature near 753 +/- 2degreesC to yield gamma-Bi2O3 and liquid. A binary eutectic occurs between Bi38ZnO58 and ZnO at a composition near 25 +/- 1.0 mol% ZnO with a melting temperature of 738 +/- 2degreesC. Based on the data obtained in this study, a revised phase diagram of the binary system Bi2O3-ZnO is proposed. (C) 2004 Kluwer Academic Publishers.